OBJECTIVE: To understand the dynamics of accommodation and presbyopia RESULTS We implanted an electrode into the Edinger-Westphal nucleus of iridectomized cynomolgus monkeys. We determined real-time dynamics of ciliary muscle, lenticular and zonular movement in response to midbrain electrical and ocular pharmacological stimulation by digital image analysis of Scheimpflug slit lamp and goniovideographic recording. Eye movements were minimized by immobilizing sutures and botulinum toxin injections into the extraocular muscles. These studies are generating new information about the mechanisms of accommodation and the validity of classical vs non-traditional models of accommodation. FUTURE DIRECTIONS Further pharmacological stimulation of accommodation will be undertaken with atropine reversal to observe the maximal movements during the stimulation and reversal of accommodation while trying to maintain absolute ocular stability. KEY WORDS ciliary muscle, lens, zonule, botulinum toxin